Powder Applications

Most industrial powders will retainyelectrical charge.

Processes and operations involving the handling of pellets, flakes, granules, powders and fine particles can often benefit from the application of electrostatics. Static electricity is a surface phenomenon and materials in particle form constitute a large total surface area to which electrostatic charge can be applied. Since most industrial powders are relatively electrically insulating, any applied charge is retained by the medium and can be used to attract, deflect, levitate, disperse or manipulate the particles.

A fully equipped powder laboratory containing electrostatic applicators, coating booths and process equipment enables Wolfson Electrostatics to undertake relatively large-scale powder handling projects. The laboratory is supplied with instrumentation enabling various measurements to be performed. Novel electrostatic powder coating techniques have already been developed using this facility. Examples of projects include application of flavourings to food, development of uniform thin-film coatings for glass and optimisation of electrostatic powder coating systems.

Powder Coating

Traditional powder coating equipmentmay not be suitable for modern materials.

Although electrostatic powder coating has been around for decades, conventional application equipment and paint technology is not well suited to coating modern materials such as plastics and composites. In addition the paint formulations may be far from optimised in terms of their propensity to acquire and retain electrostatic charge.

Wolfson Electrostatics has many years experience conducting research and development projects for the powder coating industry and can advise on issues relating to the three key areas of powder charging, transfer and deposition. Important work undertaken recently has studied novel means of charging the powder without the generation of free-ions (which can quickly charge a non-metallic surface and actually repel the paint!). Studies to improve the chargeability of paint have also been undertaken.

Particle manipulation

Particles ranging in size from a few microns (cigarette smoke) up to several millimetres (tablets, flakes, chips, shredder residue etc.) can be manipulated by electrostatic forces. These forces can be used to precipitate the particles from an air stream, separate out different media and control adhesion of particles to a surface.

Material separation particularly in the contexts of improving production yields and purifying recycling streams is an important electrostatic application. Wolfson Electrostatics’ work in this area has ranged from the design of systems to enhance the quality of agricultural products such as carob medium by removing cracked seed fragments to removal of contaminants from plastics recycling streams.

Many material handling operations generate static electricity as an unwanted by-product. This uncontrolled charge can cause a host of difficulties including flow problems, interference to electrical control equipment and even fires. In such cases the removal of charge by the application of bipolar or unipolar ions in controlled doses can alleviate the problem and ensure trouble-free operation.

Forensic Science

Identifying and examining small particles - particularly fragments of glass, paint and individual cloth fibres are of great interest to the forensic scientist. Often these particles which can provide crucially important information need to be separated from large amounts of mixed debris and this can be undertaken using electrostatics.

In a project for the UK Home office, Wolfson Electrostatics has developed a bench top system for achieving effective separation of paint chips and glass fragments from mixed debris. The system uses a pulsed electric field applied to an array of electrodes. The resultant ‘electric curtain’ effect progressively removes the debris leaving the paint particles behind.